There are known in the prior art protective helmets equipped with sound attenuating earcup assemblies which permit of communication through earphones. Assemblies of this type are adapted to protect the head of the wearer against impacts while at the same time protecting the ears of the wearer against the effect of ambient noise. Each of the earcup assemblies is provided with an earphone which permits the wearer to receive messages over a radio link or over a local communications system. One example of such a protective helmet is shown and described in Aileo U.S. Pat. No. 3,786,519, issued Jan. 22, 1974, for headgear structure.
The protective helmet shown in the Aileo patent includes an inner flexible helmet formed of a resilient material, such for example as "Nomex". It is provided with a pair of openings, each of which receives the hard sound attenuating body of an earcup assembly carrying a relatively soft sealing member adapted to engage the wearer's head around his ear. In the Aileo arrangement the construction and configuration of the helmet effects the earcup seal as the helmet is donned. More specifically, as the helmet is donned the nape is adjusted and the chin strap is secured. In the course of these operations the resilient mesh material causes the earcup assemblies to move into sealing engagement with the wearer's head. Ideally 50% compression of the ear seal against the head is achieved. The Aileo helmet comprises a hard outer shell secured to the flexible inner helmet and extending over most of the inner helmet outside the earcup assemblies.
While the earcup sealing arrangement described in the Aileo patent functions satisfactorily in the manner described above for a relatively long period of time in use of the helmet, ultimately the resilient material of which the inner helmet is formed loses its elasticity. When this occurs, adjustment of the nape and chin straps in the course of donning the helmet may actually move the earcups away from the head, thus rendering communications ineffective. The loss of resilience of the inner helmet material occurs before the helmet has outlived its usefulness as a protective helmet. It is obviously desirable that some means be provided for effecting the seal between the wearer's head and the earcup assemblies after the mesh material of the inner helmet has lost its inherent resiliency. It is further desirable that this be achieved without contacting the hard outer shell so that the acoustic isolation of the earcup assemblies can be maintained.